As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PDX - WHILE CRUISING AT FL360, FELT A VIBRATION UNDER THE CREW'S FEET (LIKE A MOTOR RUNNING) FOR ABOUT 5 SECONDS FOLLOWED BY A "CLUNK". SIMULTANEOUSLY RECEIVED A "PROX SYS FAULT" STATUS MESSAGE AND GEAR UP INDICATION FOR APPROXIMATELY 5 SECONDS AND 30 SECONDS RESPECTIVELY. SPEED WAS 260 KIAS (M .77). REMOVED AND REPLACED LANDING GEAR SELECTOR VALVE IAW AMM TASKS 32-32-10-000-801-A01 AND 32-32-10-400-801-A01. LANDING GEAR EXT/RETRACT SYSTEM OPS CK GOOD. VALVE LEAK CHECK GOOD. NO STATUS MSG NOTED, PROX SYS FAULT. RETURNED TO SERVICE.